Experimental investigation of stochastic pulsation and formation of light bullets in a laser-produced plasmas

Abstract

Generation of an extremely stable light bullets in a preformed plasma near critical density has been observed experimentally. Optical probing measurements indicate the formation of a pulsating channel, typically of about 5 /spl mu/m in diameter, directed towards to a heating laser beam, as well as a disconnected massive plasma blocks moving also towards to laser beam. The authors report time-resolved results obtained by interferometric and absorption measurements for the interaction of a 100 ps Nd:YAG laser beam at /spl lambda/=1064 nm with a metallic target in air. The formation of density ripples, light bullets and their temporal evolution was investigated with high spatial and temporal evolution. The velocity of such dense plasma blocks reaches values of order of 4.5/spl times/10 8 cm/s. And they are stable during the acceleration and propagation in air. Self-generated magnetic fields up to 8 MG were observed by means of Faraday rotation of a probe laser beam. They are "frozen"" in moving plasma blocks.